Glow discharge device having parallel permanent magnetic rod electrodes



3, 1967 SANG-CHUL KIM 3,335,311

GLOW DISCHARGE DEVICE HAVING PARALLEL PERMANENT MAGNETIC ROD ELECTRODES Filed Feb. 1, 1965 ITWVTTTOT Sang-Chub Kim 1 74.4% H HWY-neg United States Patent 3,335,311 GLOW DISCHARGE DEVICE HAVING PARALLEL PERMANENT MAGNETIC ROD ELECTRODES Sang-Chill Kim, Cleveland Heights, Ohio, assignor to General Electric Company, a corporation of New York Filed Feb. 1, 1965, Ser. No. 429,274 4 Claims. (Cl. 313-155) This invention relates in general to electric discharge devices, and more particularly to discharge devices of the cathode glow type and to the manufacture thereof.

Electric discharge devices or lamps of the well-known cathode glow type comprise a pair of cooperating electrodes placed within an enclosing envelope containing a suitable ionizable gas such as, for example, neon or argon, or mixtures thereof. In the most common types of such glow discharge devices, the electrodes are comprised of a pair of elongated metallic rods, generally of nickel, which are mounted in closely-spaced side-by-side relation within a tu u ar enclosing envelope and are coated with an activating composition or electron emissive coating comprised of oxides of the alkaline earth metals. On application of voltage across the electrodes, the device breaks doWn and a discharge is established therein between the electrodes.

The glow discharges thus established between the electrodes of such glow discharge devices heretofore have 'been subject to a certain amount of flickering which results from the. tendency of the discharge to shift back and forth along the length of the elongated electrodes. For many applications, such a flickering of the discharge is highly objectionable. In addition, where the glow discharge device is used as an indicator lamp, it is desirable that the glow discharge be localized as much as possible at the innermost or tip ends of the electrodes in order to thereby afford maximum effectiveness, for indication purposes, of the light generated by the glow discharge.

It is an object of the invention, therefore, to provide a new and improved glow discharge device which will produce in operation a substantially flickerless .glow discharge.

Another object of the invention is to provide a glow discharge device of the type having elongated rodlike electrodes in which the glow discharge is localized and maintained substantially at the innermost tip ends of the electrodes during the operation of the device.

Still another object of the invention is to provide a novel method of making a glow discharge device which, in operation, will produce a substantially flickerless glow discharge localized substantially at the innermost tip ends of the electrodes of the device.

Briefly stated, in accordance with one aspect of the invention, the elongated rod-like electrodes of a glow discharge device are permanently magnetized in opposite directions so that their innermost tip ends are of opposite polarity. The resulting lines of magnetic flux produced by the magnetized electrodes are then localized at the tip ends thereof. Since the electrons in the glow discharge which is formed between the electrodes of the device during operation tend to travel along these magnetic flux lines, the glow discharge within the device will therefore be localized and maintained at the tip ends of the electrodes where it is most desired for many applications.

Further objects and advantages of the invention will appear from the following detailed description of a species thereof and from the accompanying drawing.

In the drawing, the single figure thereof illustrates, in elevation, a glow discharge device comprising the invention and the method of magnetizing the electrodes thereof in accordance with the invention.

Referring to the single figure of the drawing, the glow discharge device 1 there illustrated comprises an elongated generally tubular shaped enclosing envelope 2 preferably provided with a smooth rounded top end 3 as shown and formed of vitreous material such as glass which is light-transmissive. Mounted within the envelope 2 is a pair of elongated wire or rod-like cold electrodes 4, 5 disposed in closely-spaced side-by-side'relation extending generally longitudinally of the elongated envelope. The electrodes 4, 5 are welded to the inner ends of respective lead-in wires or conductors 6, 7 which are sealed through a compressedend or press seal portion 8 of the envelope 2. As shown, the lower ends of the electrodes 4, 5, where they are joined to the lead-in wires 6, 7, are located closely adjacent the glass of the press 8, for example, within inch or so of the glass press. The other or innermost ends of the electrodes, however, are spaced a somewhat greater distance from the rounded end 3 of the envelope 1, for example, a distance of at least around 43 inch to inch or so from the rounded end 3. The lead-in wires 6, 7 are preferably formed of Dumet wire, that is, coppersheathed nickel-iron wire which seals readily into glass of the type conventionally employed for lamp envelopes. The electrodes 4, 5 are formed either of nickel, or nickelsheathed iron core Wire or other good paramagnetic material core wire, preferably iron, and they are coated with a suitable activating composition or electron emissive coating 9 comprised of oxides of alkaline earth metals, preferably a mixture of the oxides of barium and strontium.

The envelope 2 contains a filling of an ionizable gaseous medium, e.g., a rare gas such as neon or argon or mixtures thereof at a suitable low pressure, for instance, from 20 to 200 mm. of mercury. The gas filling is introduced into the envelope 2 through an exhaust passageway 10 which extends through the press 8 and which is closed off, following the introduction of the gas filling into the envelope, by the tipped ofif residue 11 of a glass exhaust tube (not shown) which is sealed into the press 8 during the formation thereof.

In accordance with the invention, the electrodes 4, 5 are permanently magnetized in opposite directions so that the innermost ends thereof are of opposite polarity as indicated by the letters N and S in the drawing, the inner end of one electrode being a north pole designated N and the inner end of the other electrode being a south pole designated S. The magnetization of the electrodes 4, 5 may be performed either before the sealing thereof into the envelope 2 or after the sealing thereinto. In this latter case, the magnetization of the electrodes 4, 5 may be accomplished simply by placing the glow discharge device 1, either before or after the tipping-off thereof at 11, between a pair of electromagnets 12 in the manner as shown in the drawing, with the poles of the electromagnets facing one another and of opposite polarity and with the plane of the two electrodes 4, 5 lying substantially within the plane of the poles of the electromagnets. The coils of the electromagnets 12 are then energized, by connection to a suitable source of electrical power, to effect the magnetization of the electromagnets and magnetize the electrodes.

Due to the permanently magnetized condition of the electrodes 4, 5 as described above, a constant magnetic field, disposed substantially within the interior space of the envelope, persists across the innermost ends of the electrodes, as indicated by the dotted flux lines 13 in the drawing. Since the electrons in the glow discharge 14 which forms between the electrodes 4, 5 during the operation of the glow discharge device I tend to be drawn toward the path of these magnetic flux lines 13 which are localized at the tip or innermost ends of the electrodes, the glow discharge 14 therefore will also be localized at the innermost or tip ends of the electrodes, as shown. In this manner, the glow discharge 14 is stabilized at the innermost ends of the electrodes, and is kept from flickering or shifting to various spots along the length thereof. This stabilization of the glow discharge 14 is an important feature in many of the applications for which these glow discharge devices are used. In addition, the localizing of the glow discharge at the innermost or tip ends of the electrodes 4, serves to locate the glow discharge at the top end 3 of the envelope 2 where it is thus most useful for indication purposes, as in those cases where the discharge device 1 is employed as an indicator lamp.

Because of the close proximity of the lower ends of the electrodes 4, 5 to the glass of the press 8 and the diamagnetic character of the glass, the probability of a glow discharge being formed and maintained between the lower ends of the electrodes is veryremote, despite the presence thereat of a magnetic flux linkage also, as shown in the drawing. This is so because the ions and electrons in any glow discharge tending to form at the lower ends of the electrodes 4, 5 are neutralized as quickly as they are created, due to the presence of the glass wall of the envelope 2 in the immediate vicinity of the lower ends of the electrodes. The use of nickel-sheathed iron wire for the electrodes 4, 5, instead of pure nickel, is of added advantage because of the .greater permeability of iron to magnetic fields, thereby enabling the establishment of a stronger magnetic field across the innermost tip ends of the electrodes 4, 5' for the purposes of the invention.

What I claim as new and desire to secure by Letters Patent of the United Statesis:

1. A gaseous electric glow discharge device comprising an enclosing envelope containing an ionizable gaseous medium comprising a rare gas, and a pair of elonagted closely-spaced cooperating cold electrodes in said envelope disposedin side-by-side relation and having an activating coating of oxides of alkaline earth metals, said electrodes being permanently magnetized in opposite directions to establish a localized magnetic field at their tip ends serving to localize thereat the glow discharge formed between the electrodes during operation of the device.

2. A gaseous electric glow discharge device as specified in claim 1 wherein the said electrodes are formed of material of the group consisting of nickel wire and nickelsheathed iron wire.

3. A gaseous electric glow discharge device comprising an enclosing glass envelope containing an ionizable gaseous medium comprising a rare gas, and a pair of elongated closely-spaced cooperating rod-like electrodes of magnetizable material in said envelope disposed in side-byside relation and having an activating coating of oxides of alkaline earth metals, said electrodes being permanently magnetized in opposite directions to establish a localized magnetic field at their innermost tip ends serving to localize thereat the glow discharge formed between the electrodes during operation of I the device, said electrodes being disposed in said envelope with their lowermost ends located in suflicientlyclose proximity to the glass wall of the envelope to prevent the maintenance thereat of the said glow discharge.

4. A gaseous electric glow discharge device comprising a tubular glass enclosing envelope having a rounded top end and containing an ionizable gaseous medium comprising a rare gas, and a pair of elongated closely-spaced cooperating rod-like electrodes of magnetizable material in said envelope disposed longitudinally thereof in side- 'by-side relation and having an activating coating of oxides of alkaline earth metals, said electrodes being permanently magnetized in opposite directions to establish a localized magnetic field at their innermost tip ends, adjacent the rounded top end of the envelope, serving to localize thereat the .glow discharge formed between the electrodes during operation of the device, said electrodes being disposed in said envelope with their lower ends located in sufiiciently close proximity to the glass wall of the envelope to prevent the maintenance thereat of the said glow discharge.

References Cited UNITED STATES PATENTS 1,626,646 5/1927 Thomas 313-155 X 1,965,585 7/1934 Foulke 313-185 2,824,985 2/1958 Foulke 315l X 2,900,548 8/1959 Bostick et a1 313 X JAMES W. LAWRENCE, Primary Examiner.

C. R. CAMPBELL, Assistant Examiner. 

1. A GASEOUS ELECTRIC GLOW DISCHARGE DEVICE COMPRISING AN ENCLOSING ENVELOPE CONTAINING AN IONIZABLE GASEOUS MEDIUM COMPRISING A RARE GAS, AND A PAIR OF ELONGATED CLOSELY-SPACED COOPERATING COLD ELECTRODES IN SAID ENVELOPE DISPOSED IN SIDE-BY-SIDE RELATION AND HAVING AN ACTIVATING COATING OF OXIDES OF ALKALINE EARTH METALS, SAID ELECTRODES BEING PERMANENTLY MAGNETIZED IN OPPOSITE DIRECTIONS TO ESTABLISH A LOCALIZED MAGNETIC FIELD AT THEIR TIP ENDS SERVING TO LOCALIZE THEREAT THE GLOW DISCHARGE FORMED BETWEEN THE ELECTRODES DURING OPERATION OF THE DEVICE. 